- No concurrent use of agents which may inhibit metabolism of fosaprepitant which include: cisapride, macrolide antibiotics (erythromycin, clarithromycin, azithromycin), azole antifungal agents (ketoconazole, itraconazole, voriconazole, fluconazole), amifostine, nelfinavir, calcium channel antagonists such as verapamil and diltiazem, and ritonavir.